Method for producing coated bitumen pellets



J. MOAR March 2 7, 1962 METHOD FOR PRODUCING COATED BITUMEN PELLETS Filed Nov. 14, 1958 INVENTOR. J A MOM aazasss Patented Mar. 27, 1962 3,026,568 METHOD FOR PRODUQING CQATEE) BITUMEN PELLETS Jack Moar, Edmonton, Alberta, Canada, assignor, by

mesne assignments, to Schnller Services Limited, Ed-

monton, Alberta, Canada, a corporation of Canada Filed Nov. 14, 1958, Ser. No. 773,863 4 Claims. (Cl. 18-472) The present invention relates to a method of producing bitumen pellets or granules, such as asphalt or coal tar. The term asphalt, as hereinafter used, is intended to be synonymous with and embarce coal tar.

In converting bitumen, whet-her asphalt or coal tar, into the form of finely divided pellets, granules, or droplets, it is an essential requirement to coat the pellets with an appropriate powdered mineral so as to prevent the pellets from adhering to one another. The purpose of achieving the granular form is to permit the bitumen to be handled 'in the manner of a granulated material; and if this end is to be attained it is necessary that the coating be adequately applied so as to completely eliminate any adherence of the pellets. Moreover, any method which achieves this end must be commercially practical so that the cost may be held down to a minimum. In accordance with the present invention, the method which is provided is substantially continuous With the foregoing conditions in mind, the present in vention has in view asits foremost objectve the provision of a method ofthe character indicated. which is characterized as including the basic feature of providing an upwardly directed air stream carrying the coating material in powdered form, with the asphalt being sprayed thereinto in the form of pellets or granules so as .to achieve two results. One of these is the initial coating of the pellets, and the second is a cooling which solidifies the molten asphalt.

It has been found that this initial coating of the pellets is not entirely adequate, hence the invention has in view as a further object the provision of a method of the type indicated in which a second zone of swirling aircarrying the powdered coating material is created beneath the upwardly directed stream and into which the initially coated pellets fall and pass to acquire additional coating material which supplements that supplied by the air stream' and thus give an adequate coating.

In providing a practical method of the type noted, it is important that the asphalt be in a proper molten state before it is delivered to the spray nozzle. To achieve this end, the present method provides for the recirculation of the molten asphalt as it is heated to the required temperature, whereupon the recirculation is interrupted and the molten asphalt delivered tothe spray nozzle.

After the pellets have passed through the second zone of coating material, it is important that they be collected and further cooled before being packaged. Thus another object in View is to provide, in a method of the type noted, the step of collecting and further cooling the coated pellets and then delivering them to a packaging machine.

Various other more detailed objects and advantages of the invention, such as arise in connection with carrying out the above-noted ideas in a practical'embodiment, will in part become apparent and in part be hereinafter stated as the description of the invention proceeds.

The apparatus for carrying out the novel method con sists essentially of a process tower having a spray nozzle at the top and a discharge chute at the bottom, with an upwardly directed air stream being introduced into t -e tower at the bottom and a cyclonedust. separator providing a lower zone of swirling or agitated coating material, together with an asphalt supply including 'a recirculating system which is connected to the spray nozzle by a three-way valve, a rotary cooler which is connected to the discharge chute, a supply hopper for the coating material, feed screws associated therewith, and blowers for generating the air stream and lower zone aforesaid, and a conduit system for exhausting dust from the tower and the lower end of the rotary cooler.

For a full and more complete understanding of the invention, reference may be had to the following description and accompanying drawing, wherein:

FIGURE 1 is a side view, partly in section and partly in elevation and largely diagrammatic, depicting the apparatus and method of this invention;

FIGURE 2 is a detail showing the position of the three-way valve which it assumes when delivering molten asphalt to the spray nozzle; and

FIGURE 3 is a transverse section taken on an enlarged scale through the rotary cooler.

in describing the preferred embodiment of the present invention, the materials employed, the apparatus utilized, and the method of operation will be described in that order.

The Materials The basic and essential material is asphalt or coal tar, which is preferably delivered to the processing plant in molten form so that it may be pumped into the storage tank provided thereof. The method and apparatus of this invention will be described in conjunction with asphalt, but it is to beclearly understood that the same method and apparatus embraces coal tar.

The coating material may be any of several finely ground minerals, among which are noted limestone, Portland cement, clay, mineral flour, and diatomaceous earth. For the preferred form of the invention, powdered limestone, which is commercially known as grade FF, is employed.

The Apparatus Referring to the drawing, the apparatus includes an asphalt-storage tank that is referred to in its entirety by the reference character T. The tank T has a top wall ltl a bottom it, and vertical wall or walls 12 which may be cylindrical. A delivery conduit is shown at 13 as communicating with the side wall 12, and included therein is a supply pump 14. It is intended that the conduit 13 be connected to a tank truck or other mobile supply source, and a function of the pump 14 is to pump'the asphalt from thetank truck into the storage tank T.

Disposed beneath the bottom-wall 1 1 are three gas burnerslS which provide the heat necessary to maintain the asphalt in the tank T at a required temperature. The asphalt, which is represented at 16, is preferably maintained at a tempertaure of 450 F.

Extending from the side wall 12 is another conduit 17 in which is included a strainer 18 and a circulating pump 19. From the circulating pump 19 the conduit 17 is continued upwardly to the point where it is connected with a three-way valve, which is represented diagrammatically at V. Another recirculating conduit 20 extends from the valve V to the upper end 10 of the tank as indicated at 21.

It is evident that, with the valve V in recirculating position, the molten asphalt isrecirculated by the pump 1% through tank T, strainer 18, conduit 17, valve V, and conduit 2% respectively.

A process tower is referred to in its entirety by the reference character P. This tower P comprises a. main body portion defined by a cylindrical 'wal1'22, a conical top. 23, and a conical bottom 24 which terminates in a discharge chute or spout 25.

The conical top 23 at its upper central portion communicates with a cup-shaped cap portion 25 including a top wall 26 and a cylindrical wall 27. A conduit 28 extends through the top wall 26 and at its lower end carries a spray nozzle, depicted diagrammatically at 29. The other or upper end of the conduit 28 is connected to the three-way valve V.

A large air conduit 30 has an open end that is connected to an entry port in the conical bottom 24 as indicated at 31. A smaller air conduit 32 passes through an opening in the conical bottom 24 as indicated at 33; and on its free end is mounted a cyclone dust separator, represented diagrammatically at 34. It will be noted that this cyclone dust separator 34 is located substantially within the conical bottom 24.

A supply hopper is referred to in its entirety by the reference character H, and contains a supply of powdered limestone represented at 35. Supply hopper H is open at the top, with the open top being protected by a dust hood 36. The bottom, which is represented at 37, is provided with two discharge spouts 38 and 39a, respectively. Communicating with the discharge spout 38 is a feed screw 39 having a vibrator 40 associated therewith. Feed screws of the type are commonly known as vibrascrews. A conduit 41 extends from the feed screw 39 to another conduit 42. This conduit 42 extends to a blower, represented diagrammatically at 43. The other side of the blower is connected to the conduit 30. It is evident that the vibrascrew 39, 40, together with the blower 43, and together with the conduits 41, 42, and 30, are effective to deliver an upwardly directed air stream into the tower P through the entry port 31, with the air stream carrying the powered limestone.

A second feed screw 44 is mounted below and communicates with the discharge spout 39a of the hopper H; and associated with this feed screw 44 is a vibrator 45, with the two constituting a second vibrascrew. The air conduit 32 is connected to this "ibrascrew 44, 45, and includes a smaller air blower 46. It is evident that the vibrascrew 44, 45, blower 46, and conduit 32 deliver air carrying powdered limestone to the cyclone dust separator 34.

A rotary cooler is referred to in its entirety by the reference character C and is shown in sec-tion in FIGURE 3. This cooler C comprises a cylindrical wall 47 carrying inwardly directed ribs or vanes 48 which effect a tumbling action on the material therein. The rotary cooler C is mounted in an inclined position as illustrated, and its upper end receives the lower end of the discharge chute 25 so that coated pellets coming from the discharge chute 25 are delivered into the upper end of the rotary cooler. The lower end of the rotary cooler C, which is represented at 49, is positioned over a funnel 50 that is carried at the top of a packaging machine, such as a bagger, represented at 51. This bagger delivers coated pellets to valve bags, one of which is represented at 52.

It will be noted that a dust hood 53 is positioned over the lower end 49 of the cooler C and the open top of the funnel 50. An exhaust line 54 is connected to this dust hood 53 and also to a second exhaust line 55. This exhaust line 55 is connected at one end as indicated at 56 to dust collector 57. The latter has an exhaust fan 58 associated therewith, and also has discharge spouts 59 through which collected dust is removed from the collector 57.

The other end of the exhaust conduit 55 is connected to the conduit 42 as indicated at 60. It will be noted that the conduit 42 extends to a point Where it is connected with the cylindrical wall 27 of the cap 25 as indicated at 61. A branch exhaust conduit 62 has its lower end connected to the dust hood 36 over the hopper H and its upper end to the exhaust conduit 55 as indicated at 63.

Properly positioned relative to the conical top 23 of the tower P are water sprays 64 which deliver cooling water onto the tower. Additional water sprays 65 are associated with the rotary cooler C.

The Method The asphalt is supplied to the processing plant in any appropriate manner, such as by tank trucks which deliver asphalt in molten form. Limestone in powdered from is charged into the hopper H, preferably by hand.

The molten asphalt is pumped from the tank trucks into the tank T and is maintained at a required temperature, preferably 450 F., by the gas burners 15. Before the process is actually started to produce the coated pellets, the three-way valve V is turned to the position depicted in FIGURE 1, which is the recirculating position, with the pump 19 in operation, the molten asphalt is recirculated through conduits 17, 20, and tank T.

With the asphalt circulating freely, the blowers 43 and 46 are started into operation. The vibrascrew 39 and 40 is then started to feed powdered limestone into the main air duct 30. After this is done, the three-way valve V is turned into the position depicted in FIGURE 2 in which molten asphalt is delivered to the spray nozzle 29. After the elapse of a few seconds, the second vibrascrew 44, 45 is started into operation so that the air stream created by the blower 46 delivers the air and powdered limestone carried thereby to the cyclone dust separator 34.

After the three-way valve V has been moved to the position of FIGURE 2, the recirculating conduit 20 may be cleared of asphalt by blowing steam therethrough.

It is evident that the spray of asphalt coming from the nozzle 29 encounters the upwardly directed air stream emerging from the port 31. This causes a further atomization of the asphalt which breaks the latter down into fine pellets or globules. Moreover, these pellets are initially coated by the powdered limestone or dust that is carried by the air stream and are cooled to a temperature of about 150 F. by the time they reach the lower portion of the tower. After they reach this lower portion, they fall through the lower zone of swirling or agitated air and powdered limestone carried thereby, through which they pass and in so doing acquire additional powdered limestone which completes the coating thereof.

The coated pellets now fall down the sloping sides of the conical bottom 24 and are discharged through the chute 25 into the rotary cooler C and rotated as indicated, and the ribs or vanes 48 effect a tumbling action on the coated pellets. By the time the coated pellet reach the discharge end 49 of the rotary cooler, they are at a temperature of about F.

It is evident that the temperatures in the processing tower P and the rotary cooler C may be accurately controlled through adjustment of the water sprays 64 and 65, respectively.

The packaging machine depicted at 51 may be of the flywheel-belt type, which is effective to receive the coated pellets from the discharge end 49 of the cooler and throw them through a nozzle into valve-type bags such as indicated at 52.

When the process is to be discontinued, the three-way valve V is turned to the recirculating position depicted in FIGURE 1 and the two feed screws 39 and 44 immediately shut off. The various conduits may then be blown clear with steam.

During continuation of the process, the exhaust fan 58 is maintained in operation to draw limestone dust from the cap 25 at the top of the tower P and the dust hoods 36 and 53.

While a preferred specific embodiment of the invention is hereinbefore set forth, it is to be clearly understood that the invention is not to be limited to the exact steps, constructions, and devices illustrated and described, because various modifications of these details may be provided in putting the invention into practice within the purview of the appended claims.

What is claimed is:

1. In the production of coated bitumen pellets, the method comprising the steps of (a) spraying molten bitumen downwardly into an upwardly directed stream of air carrying a powdered coating material to atomize the bitumen into fine pellets, initially coat, and partially cool the same to a semi-molten state; and (b) passing said initially coated pellets through a second zone of swirling air carrying the coating material whereby the semi-molten pellets acquire additional coating.

2. In the production of coated bitumen pellets, the method comprising the steps of (a) spraying molten bitumen downwardly into an upwardly directed stream of air carrying a powdered coating material to atomize the bitumen into fine pellets, initially coat, and partially cool the same to a semi-molten state; (b) passing said initially coated pellets through a second zone of swirling air carrying the coating material whereby the semi-molten pellets acquire additional coating; and (c) agitating and further cooling the coated pellets.

3. In the production of coated bitumen pellets, the method comprising the steps of (a) spraying molten bitumen downwardly into an upwardly directed stream of air carrying powdered limestone to atomize the bitumen into fine pellets, initially coat, and partially cool the same to a semi-molten state; and (b) passing said initially coated pellets through a second zone of swirling air carrying the coating material whereby the semi-molten pellets acquire additional coating.

4. In the production of coated bitumen pellets, the

method comprising the steps of (a) first preparing molten bitumen to a required condition by recirculation; (b) spraying the molten bitumen downwardly into an upwardly directed air stream carrying a powdered coating material to atomize the sprayed bitumen into fine pellets, initially coat, and partially cool the same to a semimolten state; (c) passing the initially coated pellets through a second zone of air carrying the powdered coating material whereby the semi-molten pellets acquire additional coating; and (d) collecting, agitating, and further cooling the coated pellets.

References Cited in the file of this patent UNITED STATES PATENTS 857,756 Raddy June 25, 1907 1,782,038 Haak Nov. 18, 1930 2,038,251 Vogt Apr. 21, 1936- 2,059,983 Dent et a1. Nov. 3, 1936 2,062,374 Noel Dec. 1, 1936 2,186,659 Vogt Jan, 9, 1940 2,276,484 Harshberger Mar. 17, 1942 2,420,368 Giordano May 13, 1947 2,484,792 Mollring Oct. 11, 1949 2,550,838 Macq May 1, 1951 2,644,769 Robinson July 7, 1953 2,938,233 Nack et a1. May 31, 1960 OTHER REFERENCES Othmer: Fluidization, Reinold Publishing Corp, N.Y. 1956, pp. 220 223. 

1. IN THE PRODUCTION OF COATED BITUMEN PELLETS, THE METHOD COMPRISING THE STEPS OF (A) SPRAYING MOLTEN BITUMEN DOWNWARDLY INTO AN UPWARDLY DIRECTED STREAM OF AIR CARRYING A POWDERED COATING MATERIAL TO ATOMIZE THE BITUMEN INTO FINE PETTELTS, INITIALLY COAT, AND PARTIALLY COOL THE SAME TO A SEMI-MOLTEN STATE; AND (B) PASSING SAID INITIALLY COATED PELLETS THROUGH A SECOND ZONE OF SWIRLING AIR CARRYING THE COATING MATERIAL WHEREBY THE SEMI-MOLTEN PELLETS ACQUIRE ADDITIONAL COATING. 